GH-97950: Use new-style index directive ('builtin') (GH-104164)
* Uncomment builtin removal in pairindextypes
* Use new-style index directive ('builtin') - C API
* Use new-style index directive ('builtin') - Extending
* Use new-style index directive ('builtin') - Library
* Use new-style index directive ('builtin') - Reference
* Use new-style index directive ('builtin') - Tutorial
(cherry picked from commit f5088006ca)
Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>
Use an unique identifier for the different grammars documented using
the Sphinx productionlist markup.
productionlist markups of the same grammar, like "expressions" or
"compound statements", use the same identifier "python-grammar".
Document extended iterable unpacking, raising and catching exceptions, class decorators, etc.
A few notable things are not documented yet, I've added XXX comments about that.
